The present invention relates to a novel and improved material useful as a building sheet material, such as roofing shingles, siding or the like. More particularly, this invention relates to a bituminous sheet material comprising an inorganic fiber mat substrate saturated with a bituminous composition, which sheet material possesses improved physical properties for handling and durability, particularly in lower temperature environments.
Bituminous sheet materials, such as roofing felt or shingles which are useful in sealing exterior building surfaces, are generally composed of a support layer or substrate, traditionally a felted, fibrous membrane which is saturated with a water-proofing agent, such as an asphalt or bituminous composition. While the asphalt or bitumen is still in a plastic state, granular materials which are opaque to ultraviolet light are ordinarily pressed therein on the weather-exposed face to protect the bitumen from the ultraviolet rays or actinic effects of the sun, as well as to form a decorative coating. The granular material further acts to protect the asphalt or bitumen coating which would otherwise deteriorate producing cracking or crazing, thus permitting leaking of the roof or siding surface in due time. The granules which have been most widely used are formed from rock, such as crushed slate and trap rock.
The felted fibrous substrate or membrane has been most commonly formed of rag, wood, paper, jute or other organic fibers on a machine similar to that used for manufacturing paper. The felt material is impregnated with asphalt, generally a blown petroleum derivative, by immersion, flowing, spraying, roller coating, or by a combination of such treatments, with excess saturant removed by scraping. The waterproofing character of the asphalt is the main attribute of the final product and the felt serves in a secondary status as a carrier, substrate and preserver of the asphalt.
While sheet materials based on organic felts possess excellent flexibility and tensile properties for good handling characteristics, they tend either to absorb or release moisture under varying climatic conditions. The resulting fluctuations in moisture content cause the felt to expand and contract, which often results in the occurrence of blisters due to steam occlusions. Organic fibers used in making suitable felt materials also tend to decay somewhat rapidly under variations in weather conditions and have drawbacks for other reasons, such as heat and hydro-dimensional instability which lead to distortions in the applied finished product.
Accordingly, it has been desirable to use inorganic fibers in preparing roofing felts, and particularly glass fibers, since such fibers possess excellent thermal and chemical stability. The desirability of an inorganic or glass fiber based felt is due to its peculiar properties and characteristics, including fire-resistance, low thermal expansion and contraction, insensitivity to relative humidity changes, and resistance to moisture absorption.
While glass fibers are more weather resistant then organic fibers, glass fiber mat based shingles coated or impregnated with a bituminous material have heretofore had serious application and handling problems, particularly when installed at or below a field ambient temperature of 40.degree. F. (4.5.degree. C.). Moreover, the inherent brittleness of most inorganic or glass fiber mat materials, which is less of a problem in milder climates, makes the product totally unsuitable in colder climates.
While glass fiber mat of better quality, particularly as to flexibility, may be prepared from continually drawn glass fibers cut from higher quality glass staple fiber, the cost of any resulting product increases significantly. To keep costs at an acceptable level, less expensive glass fibers and other inorganic fibers, such as glass wool and rock wool are desirable. However, inorganic fibers other than glass are even more brittle and flexibility is further impaired.
A number of attempts have been made to improve the flexibility, durability, and handling characteristics of inorganic fiber based mat products. The flexibility of such products can be enhanced by use of a special flexible glue or binder, but the resulting product has been found to have considerably lower breaking or tensile strength. Since glass fiber mats are composed of glass fibers held together by a binder material, attempts have been made to produce glass fiber mat having improved tensile strength and flexibility by varying the binder composition. A multitude of compositions comprising the asphalt or bitumen component combined with elastomer and thermoplastic polymer ingredients have been used as binders, but unfortunately, all have heretofore been deficient in one or more respects.
Bituminous coating or binder materials suitable for most roof service conditions have a glass transition point of approximately 32.degree. F. (0.degree. C.). Commonly, the bituminous materials are filled with an inorganic mineral stabilizer to improve their fire resistance, high temperature flow and weather resistance. These filled bituminous coatings, however, have a distinct tendency to shatter and break during normal application or handling or during maintenance traffic on the roof shingle surface. In particular, such binder materials provide glass mats which exhibit only acceptable tensile strengths at room temperature and at lower temperatures. Furthermore, the tensile strengths of such mats deteriorate appreciably when the mats are subjected to wet conditions, which can be encountered in their use in roofing as well as in siding or flooring products. In addition, these prior art mats have relatively poor flexibility resulting in buckling, creasing or cracking of the mats during use, handling or application as a base in asphalt roofing shingles or as a backing felt or base support for other sheet uses.
Accordingly, it is an object of the present invention to provide an inorganic fiber based mat composition, particularly, a glass fiber mat roofing felt, having improved flexibility, tensile strength, durability and handling properties, particularly at lower temperatures.
It is another object of this invention to provide an all weather glass mat based bituminous roofing felt which has acceptable physical properties, including flexibility and tensile strength, at both high and low temperature extremes, and which is capable of withstanding the stresses imposed by an outdoor environment, particularly the mechanical stresses due to the motion of the surface on which it is applied, natural atmospheric stresses (due to temperature, sun and the like) and artificial stresses, such as chemical and physical attacks.